During channel demodulation, if a terminal can acquire some statistical characteristic parameters of a channel between a base station and the terminal in advance, the terminal may effectively utilize these statistical characteristic parameters to improve estimation accuracy of a demodulation reference signal, improve receiver performance, and effectively suppress noise. The terminal may apply the statistical characteristic parameters to different estimation algorithms and receiving algorithms. It should be noted that such statistical channel characteristics can be accurately measured by virtue of reference signals sent by the same base station, that is, these statistical characteristic parameters are usually measured based on reference signals, for example, a Channel State Information Reference Signal (CSI-RS) or a Cell specific Reference Signal (CRS), sent by the same base station.
In addition, when a base station sends a signal, components in the base station may not be ideal and introduction of errors is inevitable, so that the problems of frequency deviation and time deviation in a practical system are unavoidable. Generally speaking, calibration of frequency deviation and time deviation can be completed based on measurement performed through CSI-RSs or CRSs sent by the same base station.
In a Long Term Evolution (LTE)/Long Term Evolution-Advanced (LTE-A) system, when multipoint transmission is supported, since a base station sending data is transparent for a terminal and the base station sending the data may be dynamically switched, the terminal can not accurately learn about the specific base station sending the data received by the terminal. Therefore, a definition and notification signaling of a quasi-co-location indicator are introduced.
A quasi-co-location indicator indicates that a CSI-RS sent and notified by current data and a CSI-RS sent and notified by a dedicated de-Modulation Reference Signal (DMRS) are quasi-co-located, and the two sent and notified CSI-RSs have approximately the same large-scale characteristic of a channel, for example, delay spread, Doppler spread, Doppler shift and average delay. The CSI-RSs being quasi-co-located represents that the current data and the DMRS are sent approximately by the same base station. In the standard 3rd Generation Partnership Project (3GPP) TS 36.213, a quasi-co-location indicator and Resource Element (RE) mapping related information are jointly notified. Table 1 shows a meaning of each state of quasi-co-location indicator and data channel RE mapping notification signaling.
TABLE 1Meaning of Each State of Quasi-Co-Location Indicatorand Data Channel RE Mapping Notification SignalingValue of ‘Physical Downlink SharedChannel (PDSCH) RE Mapping andQuasi-Co-Location Indicator’ fieldDescription‘00’Parameter set 1 configuredby higher layers‘01’Parameter set 2 configuredby higher layers‘10’Parameter set 3 configuredby higher layers‘11’Parameter set 4 configuredby higher layers
As shown in Table 1, in the quasi-co-location indicator and data channel RE mapping notification signaling, 2 bit physical-layer Downlink Control Information (DCI) is adopted to dynamically indicate up to 4 parameter sets, each set including a set of parameters. The set of parameters may include the following multiple types of information:                configuration parameter information of a CRS, including parameters such as the ports count and a frequency domain shift;        Multimedia Broadcast multicast service Single Frequency Network (MBSFN) subframe configuration parameter information;        parameter configuration information of a Zero Power (ZP) CSI-RS;        configuration information of a data channel start symbol parameter; and        quasi-co-location Non-Zero Power (NZP) CSI-RS information.        
It can be seen that, when a base station sends data to a terminal, the base station may be dynamically switched. An RE mapping problem and a problem of change of a quasi-co-location of reference signal and data transmission may be solved by dynamically indicating the abovementioned information through the 2 bit signaling.
In earlier versions, CSI-RSs are all non-precoding reference signals, so that a base station usually sends only one set of CSI-RSs. However, due to increase of reference signal and feedback overhead, after precoding CSI-RSs are introduced, there may be a situation in which the same base station sends multiple precoding reference signals. Since different precoding reference signals correspond to different precoding weights respectively, the use of multiple precoding reference signals equivalently generates multiple virtual cells. FIG. 1 is a schematic diagram illustrating the generation multiple virtual cells under the condition of different precoding reference signals.
Different precoding reference signals are supported in the following manners.
A first manner:
Table 2 shows a condition in which different precoding reference signals explicitly correspond to multiple sets of different reference signal configurations.
TABLE 2Different Precoding Reference Signals Explicitly Correspondto Multiple Sets of Different Reference Signal ConfigurationsNZP CSI-RSPrecoding referencePrecodingconfiguration 1signal 1weight1/Beam 1NZP CSI-RSPrecoding referencePrecodingconfiguration 2signal 2weight1/Beam 1. . .. . .. . .NZP CSI-RSPrecoding referencePrecodingconfiguration Nsignal Nweight1/Beam N
A second manner:
Table 3 shows a condition in which different port groups under the same set of NZP CSI-RS configuration correspond to precoding reference signals with different weights.
TABLE 3Reference Signals on Different Port Groups under the SameSet of NZP CSI-RS Configuration Correspond to PrecodingReference Signals with Different Weights respectivelyNZP CSI-RSPortPrecoding referencePrecodingconfiguration igroup 1signal 1weight1/Beam 1PortPrecoding referencePrecodinggroup 2signal 2weight1/Beam 2. . .. . .. . .PortPrecoding referencePrecodinggroup Nsignal Nweight1/Beam N
A third manner:
Table 4 shows a condition in which reference signals on different subframes under the same NZP CSI-RS configuration i correspond to precoding reference signals with different weights respectively.
TABLE 4Reference Signals on Different Subframes under the SameNZP CSI-RS Configuration i Correspond to Precoding ReferenceSignals with Different Weights respectivelyNZP CSI-RSSubframe aPrecoding referencePrecodingconfiguration isignal 1weight1/Beam 1Subframe bPrecoding referencePrecodingsignal 2weight1/Beam 2. . .. . .. . .Subframe nPrecoding referencePrecodingsignal Nweight1/Beam N
A fourth manner:
Table 5 shows a condition in which reference signals at different frequency domain positions under the same set of NZP CSI-RS configuration i correspond to precoding reference signals with different weights respectively.
TABLE 5Reference Signals at Different Frequency Domain Positionsunder the Same Set of NZP CSI-RS Configuration i Correspondto Precoding Reference Signals with Different WeightsNZP CSI-RSSub-band aPrecoding referencePrecodingconfiguration isignal 1weight1/Beam 1Sub-band bPrecoding referencePrecodingsignal 2weight1/Beam 2. . .. . .. . .Sub-band nPrecoding referencePrecodingsignal Nweight1/Beam N
Thus, it can be seen that downlink quasi-co-location indicator and data channel RE mapping notification signaling supports notification of only one set of NZP CSI-RS configuration for quasi-co-location binding with a data channel which is transmitted at present. However, for the second, third or fourth manner, notification of related quasi-co-location information cannot distinguish between different ports, different subframes and different sub-bands (frequency domain), so that the adoption of these manners may influence channel estimation performance and receiver performance. Moreover, for the first, second, third or fourth manner, when multiple beams are present in a cell, multiple virtual cells shown in FIG. 1 may be formed, and under such a circumstance, the 2 bit downlink quasi-co-location indicator and data channel RE mapping notification signaling may not meet a requirement.
For the problem that a large-scale characteristic of a channel acquired by a terminal is inaccurate due to indefinite indication in quasi-co-location information notification signaling, there is yet no solution at present.